The invention described herein relates to explosive compositions and more particularly to composite explosive systems containing mixtures of ammonium nitrate and ammonium salts of nitroheterocycles.
The rate at which an explosive decomposes into its detonation products influences its performance because of the effect on the pressure and velocity of the detonation wave. Performance is also related to the kinds and amounts of the decomposition products, their rate of formation, and the energy released in forming them. Whether particular effects help performance or degrade it depends on the application to which the explosive is to be put.
Although there are certain exceptions to the general rule, an ideal explosive has been defined as one which has a decomposition rate rapid enough to be thought of as nearly instantaneous or time-independent. Most of the final products are formed by a thin, fast-moving reaction zone. Parameters such as detonation pressure and velocity can be quite well calculated on that basis, especially for condensed-phase CHNO explosives, by calibrated codes and formulas which are well known in the art.
In nonideal explosives reaction rates are usually slower, and either important amounts of chemical reaction go on well after the end of the steady-state detonation or the zone is temporally very long. Generally, detonation pressures and velocity, and hence power, are lower in nonideal explosives than in ideal explosives. As but one example, calculations based on ideal behavior predict that a mixture of HMX and lithium perchlorate should give 110% of the performance of pure HMX. However, a cylinder test showed the performance of the mixture to be significantly less than that of the pure HMX.
Presumably, by varying the reaction and pressure/time characteristics within the total reaction zone, i.e., the detonation zone terminated by the Chapman-Jouguet plane plus the reactive region behind it, it should be possible to optimize the performance of nonideal explosives. Unfortunately, heretofore efforts to make nonideal explosives behave more "ideally", i.e., more like ideal explosives, have at best met with mixed success.
Nonetheless, nonideal energetic explosives have a significant advantage over many ideal explosives in that they can frequently be made from relatively cheap and plentiful materials, with ammonium nitrate (AN) being perhaps the best example. Nonideal explosives are usually composites, i.e., mixtures of particulate oxidizers and fuels. They may contain an ideal explosive as an ingredient. Well-known examples of nonideal explosives are ANFO (ammonium nitrate/fuel oil) and Amatex (ammonium nitrate/TNT/RDX).
It is apparent from the foregoing that it would be highly desirable to provide explosive systems of the type which have traditionally been considered nonideal explosives but which have the characteristics of ideal explosives. In particular, it would be advantageous if such explosive systems could incorporate ammonium nitrate as a primary ingredient.
It is known that the performance of nonideal explosives can be improved by more intimate incorporation of the components. Thus, for example, mixtures of gelled nitromethane with 200 .mu.m particles of ammonium perchlorate are distinctly nonideal whereas mixtures containing 5 .mu.m ammonium perchlorate are nearly ideal in their performance.
While it has been assumed that maximum performance can be obtained when components are combined in a continuous solid solution, heretofore no cost-effective, practical, solid-solution system has been found. Cosolidification of AN with amine nitrates, in an attempt to promote eutectic formation by the common nitrate ion, while substantially improving performance has not rendered it ideal in any explosive system thus far disclosed in the literature.
Accordingly, it is an object of this invention to provide novel explosive systems.
Another object is to provide nonideal explosive systems which perform substantially as ideal explosives.
Yet another object is to provide novel explosive systems containing ammonium nitrate as a primary ingredient.
Still another object is to provide novel explosive systems containing ammonium nitrate which act as ideal explosives.
A further object is to provide novel explosive systems containing ammonium nitrate as a primary ingredient which are castable.
Other objects, advantages and novel features of the invention will become apparent to those skilled in the art upon examination of the following detailed description of a preferred embodiment of the invention and the accompanying drawings.